High-temperature lubricating greases



Patented Apr. 1, 1952 UNITED STATES PATENT OFFICE HIGH-TEMPERATURE LUBRICATING GREASES No Drawing. Application September 30, 1950, Serial No. 187,829

v 17 Claims.

This invention relates to high temperature lubricating grease compositions and to a process for their manufacture. Particularly this inven-- tion relates to high temperature lubricating grease compositions prepared by incorporating into a lubricating oil the metal soap of a high molecular weight substantially saturated fatty acid and the reaction product obtained by reacting a metallic hydroxide with a material selected from the group consisting of acrolein and acrolein dimer.

' It has previously been found that, for some purposes, it is advantageous to combine certain metal salts of relatively low molecular weight acids with the metal soaps ordinarily employed as thickeners for lubricating grease compositions. It has been suggested that the addition of the salts of the low molecular weight acids to the relatively high molecular weight soaps results in the formation of a complex of salt and soap which furnishes a superior thickening effect and improves the stability of the composition, particularly at high temperatures. It is also felt that the provision of a lower organic salt tends to offset a normal tendency of some of the soaps of certain of the higher fatty acids, especially the more unsaturated acids, to break down into lower molecular weight substances having little or no thickening power.

Whatever may be the phenomena involved, the addition of salts and the like, of relatively low molecular weight compounds appears to be ad vantageous, especially in alkali and alkaline earth metal base greases. These materials, in many cases at least, improve the physical structure of the greases and are particularly useful instabilizing them structurally at elevated temperatures. Greases containing them appear to be quite'susceptible to further stabilization by conventional oxidation inhibitors.

Although various low molecular weight compounds have been proposed recently, such as the salts of acetic and propionic acids and certain of the lower unsaturated acids, such as acrylic'and crotonic acid, andthe like, as being particularly useful as grease modifiers, these materials are not always suitable, and some are relatively expensive.

It has-now been found that quite satisfactory hightemperature lubricating greases may be prepared by thickening a lubricating oil to a grease consistency with a mixture of the metal soap of a high molecular weight substantially saturated fatty acid and a modifier consisting of the reaction product obtained by subjecting a material selected from the class consisting of acrolein,

H This compound, which recently became avail able commercially, is a volatile material and, since it has a highly reactive hydrogen atom on the alpha carbon will not undergo th Cannizzaro reaction to give the acid salt and th alcohol in the presence of a strong alkali. On heating in the presence of a polymerization inhibitor, such as hydroquinone, a dimer is formed from two molecules of the monomer and has the following structural formula:

C CH:

CHO

This dimer is technically described as 3.4-dihydro-2I-l-pyran-2-carboxaldehyde.

The high temperature grease compositions of this invention may be prepared by followingone of the two procedures listed below:

(1) The desired amount of the acrolein or acro-' lein dimer containing a polymerization inhibitor is admixed with one of two parts of the lubricating 1 oil to beused as the liquid phase of the grease composition. Ordinarily there will be added to the oil from 5 to 10 weight percent of the acrolein or the acrolein dimer. However, weight percentages within a range of from 2 to 20 percent may be.

used to obtain a satisfactory grease composition. Thereafter there is added to the mixture with agitation a strong metallic hydroxide solution. If,

desired, sufiicient of the solution to react with the acrolein or acrolein dimer alone may be added. In these circumstances, from about 2.5 to 5.0 weight percent, based on the acrolein or acrolein dimer used; of the 'base will be added. If it is desired, however, sufiicient of the metallic hydroxide solution may be added at this stage to completely saponify the fatty material, or soap base which is added later. 1

Upon the addition of the solution of the metallic hydroxide to the mixture of lubricating oil containing the acrolein or acrolein dimera reaction takes place as indicated by a temperature rise. The reaction products remain dissolved in the oil. After the reaction subsides, the desired amount of a substantially saturated fatty acid is then added and, if necessary, additional metallic hydroxide solution to completely saponify the fatty acid. The temperature is then raised to about 250 to 275 F. to dehydrate the mixture, the balance of the lubricating oil added, and the temperature raised again to about 475 to 500 F. until all of the ingredients are in solution in the oil. The resulting mixture is then cooled by any of the well known grease COOIiIlg methods (2) To one of two portions of the lubricating oil used as the liquid phase of the grease composition there is added the desired amount of the acrolein or acrolein dimer, the desired amountof the metallic hydroxide solution, and the substantially saturated fatty acid. The temperature is raised to about 225 to 275 F. and the balance of the lubricating oil is added. After heating the total mixture to about 475 to 500 F., it is allowed to cool in any of the commonly known grease cooling procedures.

It is to be seen that these two procedures involve either the formation of the reaction product in oil and a subsequent addition of the soap making materials or a simultaneous reaction between the acrolein or acrolein dimer and the metallic hydroxide and the saponification of the fatty acid. For some purposes, either of these procedures may be preferred.

It is also within the concept of this invention to add a preformed soap to the oil solution containing the reaction product as outlined in procedure 1.

The relative proportions of the high molecular weight soaps and the acrolein/acrolein dimermetallic hydroxide reaction product, prepared as described above, may be varied rather widely. Broadly, molecular proportions of about 1 to 4 parts of soap to l to 4 parts of the reaction product may be used, equimolar proportions being preferred. The total quantity of these ingredicuts to be used in a given grease composition will vary depending upon the type of grease desired. For a very hard grease the proportions of total thickener, that is, soap plus reaction product, may approach 50%, whereas for a soft grease 5% of total thickener may be used, the percentages given being by weight, based on the weight of the total composition. Generally speaking, the greases of invention will consist of a lubricating oil containing from 3% to by weight of the metal soap of a substantially saturated high molecular weight fatty acid and from 2% to 20% of the reaction products obtained by reacting the metallic hydroxide with acrolein or acrolein dimer.

As the high molecular weight fatty acid used to form the metal soap, any of the well known saponiflable fatty materials known to the art are operable. Grease making materials such as the hydrogenated fish oil acids, stearic acid; oleic acid, hydroxy stearic acid, beef-fat, tallow, the saturated or unsaturated glycerides of various fatty acids, or mixtures of these in any proportion are operable. The preferred embodiment contemplates the use of substantially saturated fatty acids containing from about 12 to 22 carbon atoms.

As to the metallic hydroxide used to form the soap and the reaction products, it is preferred to use sodium hydroxide; Lithium based greases may be prepared using lithium hydroxide as may greases of calcium, barium or strontium. Mixed base greases are also prepared according to the instant procedure.

As to the liquid phase of the grease composition, the mineral base lubricating oils are preferred, ranging in viscosity from 35 to 1,000 S. U. S. at 210 F. The invention is not limited, however, to the use of mineral base oils, since various synthetic oils may also be used as a part or all of the liquid phase of the grease. Certain of the synthetic esters, such as di-2-ethylhexyl sebacate, and esters of other dibasic acids such as adipic acid esters, as well as polymerized cracked wax, alkylated aromatic, polyglycol ethers, polyglycol esters and various combinations of theabove may be used.

The invention will be more fully explained by reference to the following specific examples.

Example I Formulation: Wt. percen Acrolein 7.6 Sodium hydroxide (33 aqueous solution) 5.0 Hydrogenated fish oil acids 11. Phenyl alpha naphthylamine 1.0 Mineral lubricating oil 74.9

The acrolein, the fish oil acids, and the sodium hydroxide solution were added to one-half of the mineral oil and mixed without heating for a short period (30 minutes), then the mass was heated with agitation to 250 F. When this temperature had been reached the balance of the mineral oil and the phenyl alpha naphthylamine were added and the heating continued to a temperature of 475 F. The mixture was then cooled in the kettle while stirring to room temperature and there resulted an excellent smooth product having a high dropping point and excellent structural stability.

- Inspection data on the grease of Example I are as follows:

Penetration: (77 F. in mm./l0)-- 3,4-dihydro-2H-pyran-2-carboaxaldehyde (acrolein dimer) 7.6 Sodium hydroxide 4.5 Hydrogenated fish oil acids 11.5 Phenyl alpha naphthylamine 0.8 Mineral lubricating oil 75.6

The acrolein dimer and one half of the oil were mixed together at F; While stirring vigorously a 33 aqueous solution of sodium hydroxide was added. The temperature of reaction'rose slowly to F. and subsided. During this reaction some crystalline material precipitated out of solution but as the temperature of reaction rose the material redissolved. The total reaction material was then added to the preformed sodium soap of the fish oil acids neutralized with sodium hydroxide in the remain der of theoil. The total mass was heated to 360 F. while stirring. On cooling a portion of the mass a solid product having an excellent stable grease structure was obtained. Continued heating of the total mass causedsome foam formation but little thickening or thinning out of the product Penetration: (77 F. in him/)- Worked penetration-GO strokes 180 Worked penetration60,000 strokes (fine hole worker plate) 310 Dropping point, F. 500+ AS'IM free alkalinity, percent as oleic acid 0.3

What is claimed is:

1. A process of preparing a lubricating grease composition having outstanding utility at ele vated temperatures which comprises the steps of combining with one of two portions of a lubricating oil to be used as the liquid phase, from 1 to 4 molar proportions of a material selected from the class consisting of acrolein, acrolein dimer and mixtures of acrolein and acrolein dimer, adding to the mixture with agitation an aqueous solution containing from 2.5% to 5% by weight, based on the weight of the material of the class of a metallic hydroxide, thereafter adding from 1 to 4 molar proportions of a. substantially saturated fatty acid containing from 12 to 22 carbon atoms per molecule, and additional metallic hydroxide solution to insure complete saponification of said fatty acid, raising the temperature of the resulting mixture, adding the second portion of the lubricating oil, and cooling the resulting mixture to obtain a finished grease composition.

2. A process of preparing a lubricating grease composition having outstanding utility at elevated temperatures which comprises the steps of combining with one of two portions of a lubri-- cating oil to be used as the liquid phase, from 1 to 4 molar proportions of a material selected from the class consisting of acrolein, acrolein dimer and mixtures of acrolein and acrolein dimer, adding to the mixture with agitation an aqueous solution containing from 2.5% to 5% by weight, based on the weight of the material of the class of a metallic hydroxide, thereafter adding from 1 to 4 molar proportions of a substantially saturated fatty acid containing from 12 to 22 carbon atoms per molecule, and additional metallic hydroxide solution to insure coniplete saponification of said fatty acid, raising the temperature of the resulting mixture to about 225 to 275 F. to dehydrate, adding the second portion of the lubricating oil, heating further to 4'75 to 500 F., and cooling the resulting mixture to obtain a finished grease composition.

3. A process according to claim 2 wherein said material is acrolein.

4. A process according to claim 2 wherein said material is acrolein dimer.

5. A process according to claim 2 wherein said metallic hydroxide is a material of the class consisting of sodium, lithium, calcium, barium, and strontium hydroxides.

6. A process according to claim 1 wherein said metallic hydroxide is sodium hydroxide.

7. ;A process according to claim 2 wherein equimolar proportions of acrolein and said substantially saturated fatty acid are used.

8. A process of preparing a lubricating grease composition having outstanding utility at elevated temperatures which comprises the steps of combining with one of two portions of a mineral lubricating oil to be used as the liquid phase from 2 to 20 weight percent of a material selected from the class consisting of acrolein andacrolein dimer, from 3 to 30 weight percent of a substantially saturated fatty acid containing from 12 to 20 carbon atoms per molecule and from 0.9 to 9.0 weight percent of an aqueoussolu tion of a metallic hydroxide, raising the temperature of the mixture to one within a range of from 225 to 275 F., adding the second portion of said mineral'oil, again raising the temperature of the mixture to about 475 to 500 F. and cooling the resulting mixture to obtain a finished grease composition.

9. A process according to claim 8 wherein said material is acrolein;

10. A process according to claim 8 wherein said material is acrolein dimer.

11. A process according to claim -8 wherein said metallic hydroxide is sodium hydroxide.

12. A lubricating grease composition consisting essentially of a mineral lubricating oil thickened to a grease consistency withfrom 5% to 50% by weight based on the weight of the total composition of a combination of from 1 to 4 molar proportions of a metallic soap of a substantially saturated fatty acid containing from 12 to 22 carbon atoms, with from 1 to 4 molar proportions of a reaction product of a metallic hydroxide and a material selected from the class consisting of acrolein and acrolein dimer, said reaction product being obtained by reacting said material with about 2.5% to 5% by weight, based on the weight of the material of the class of said metallic hydroxide in the presence of a portion of said lubricating oil.

' 13. A lubricating grease composition according to claim 12 wherein said material is acrolein.

14. A lubricating grease composition according to claim 12 wherein said material is acrolein dimer.

15. A lubricating composition according to claim 12 wherein said metallic hydroxide is sodium hydroxide.

16. A lubricating grease composition having the following formulation:

7.6 weight per cent acrolein dimer 4.5 weight per cent sodium hydroxide 11.5 weight per cent hydrogenated fish oil acids 0.8 weight percent phenyl alpha naphthylamine,

and 75.6 Weight per cent mineral lubricating oil said composition having been prepared by combining with one of two portions of the lubricating oil of an acrolein dimer, adding to the mixture with agitation the sodium hydroxide in the form of an aqueous solution, thereafter adding the hydrogenated fish oil acids, raising the temperature of the resulting mixture to about 225 F. to 275 F. to dehydrate, adding the second portion of the lubricating oil, heating further to 475 F. to 500 F. and cooling the resulting mixture to obtain the finished grease composition.

17. A lubricating grease composition havin the following formulation:

7.6 weight per cent acrolein 5.0 Weight per cent sodium hydroxide 11.5 weight .per cent hydrogenated fish oil acids 1.0 weight per cent phenyl alpha naphthylamine, and 74.9 weight per cent mineral lubricating oil said composition haying b'een prepared by oo m-. EEFERENCES CITED bining with one of two portions oi the lub t- The following references are of record in the ing oil .of the acrolein, the hydrogenated fish oil file of this patent: acids. and the sodium hydroxide in the form of an aqueous solution, raising the temperature of 5 UNITED STATES PATENTS the mixture to one within a range of from 225 Number Name Date F to 27.5 F., adding the second portion of the 2,182,137 Rieketts D c. 5, 1939 mineral oil again raising the temperatiire-v of 2,516,137 Morway et a1 July 25,1950

the-mixture-to about 4575" F. to 500 F. and cooling the resulting mixture to obtain a finished i0 grease composition.

ARNOLD J. MORWAY. i ALFRED H. MATUSZAK. 

1. A PROCESS OF PREPARING A LUBRCATING GREASE COMPOSITION HAVING OUTSTANDING UTILITY AT ELEVATED TEMPERATURES WHICH COMPRISES THE STEPS OF COMBINING WITH ONE OF TWO PORTIONS OF A LUBRICATING OIL TO BE USED AS THE LIQUID PHASE, FROM 1 TO 4 MOLAR PROPORTIONS OF THE MATERIAL SELECTED FROM THE CLASS CONSISTING OF ACROLEIN, ACROLEIN DIMER AND MIXTURES OF ACROLEIN AND ACROLEIN DIMER, ADDING TO THE MIXTURE WITH AGITATION AN AQUEOUS, SOLUTION CONTAINING FROM 2.5% TO 5% BY WEIGHT, BASED ON THE WEIGHT OF THE MATERIAL OF THE CLASS OF A METALLIC HYDROXIDE, THEREAFTER ADDING FROM 1 TO 4 MOLAR PROPORTIONS OF A SUBSTANTIALLY SATURATED FATTY ACID CONTAINING FROM 12 TO 22 CARBON ATOMS PER MOLECULE, AND ADDITIONAL METALLIC HYDROXIDE SOLUTION TO INSURE COMPLETE SAPONIFICATION OF SAID FATTY ACID, RAISING THE TEMPERATURE OF THE LUBRICATING OIL, AND COOLSECOND PORTION OF THE MIXTURE TO OBTAIN A FINISHED GREASE COMPOSITION. 